more alpha input circuit talk
-
>>The Alpha type circuit provides low swr to the exciter,
: Not low enough for transistor radios unless
: a tuner is used.
-
Based on all the examples I've seen, the swr is low
enough for most radios.
-
>is also relatively broadband, is low in cost and physical -
>mechanical part requirements and easy to install.
-
: The tradeoff of having no flywheel is not small. -
-
True but it was a relative trade off Alpha felt would
work, and it does to a point.
-
: Two 8874s in parallel have a driving Z of roughly half
: of 26-ohms at the negative V peak. This requires
: matching with a Pi-network/flywheel.
-
Since this thread started, I tried to locate the magic
drive Z value with mixed bag and varied results. An
amps member reported ~95 ohms for a single tube,
a W6SAI Radio Handbook says ~160 ohms and now
your 2 tube value. Someone has to have the real value,
it's not listed anywhere in plain sight on the Eimac data
sheet I just looked up on the web.
-
The single tube ~95 ohm Z value works with the other
circuit values in the Alpha circuit diagram.
-
>The alternate half cycle is (for the example) pretty much
>just the resistor network and some C. So the toroidal rf
>xmfr secondary "load" halves.
-
: What is the swamper resistance?
-
The Alpha 274 (two hole version) has a total parallel
swamp R value of 47 ohms as reported on the diagram.
The R network value in parallel with the 47.5 ohm dynamic
tube Z works out the 23.6 ohms. The toroid secondary
value is reported to be 22.2 ohms.
-
: With solid-state radios, sans-tuner, the SWR usually
: needs to be 1.2:1 or better to avoid power foldback. A
: swamper/transformer is not capable of that.
-
Without getting into an argument, I will say that many if
not most of my common transceivers will drive into swr
levels higher than 1.2:1 without a problem.
-
>It would not provide flywheel, just "better" exciter
>matching in the alternate half cycle.
-
: Exactamente
-
Better matching and the broad band response were
the desired results, above a flywheel effect. I would
say the engineering goal was reached with the expected
results.
-
skipp
________________________________________________________________
GET INTERNET ACCESS FROM JUNO!
Juno offers FREE or PREMIUM Internet access for less!
Join Juno today! For your FREE software, visit:
http://dl.www.juno.com/get/web/.
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|